Coaxial connector with impedance control

ABSTRACT

Coaxial connector provided with a body (20) of electroconductive material which extends in the casing (1) of the connector between the connection ends (18, 19) and is electrically separated therefrom. The body (20) functions as a capacitive coupling medium between the connection ends (18, 19) and thus influences the electrical connection impedance of the connector. Because a body of magnetic material (21) is accommodated at the same time, an inductive coupling can be provided and frequency-dependent impedance matching is possible.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a coaxial connector provided with at least oneelectrical contact element having a contact side in the form of acoaxial inner and outer contact member for making contact with a furtherconnector, and having a connection side in the form of connection ends,which extend from the inner and outer contact member, for connectingelectrical wiring.

2. Brief Description of the Related Art

Coaxial connectors are in practice used on a large scale forradio-frequency (RF) connections in radio and television sets,telecommunication equipment such as telephone sets and the like. Twomain groups can be distinguished, i.e. connectors for mounting on aprinted-circuit board and cable connectors. In the case of theconnectors for mounting on a printed circuit board, a furtherdistinction can be drawn between connectors with connection ends forso-called surface mounting and connectors with connection ends formounting in a hole in the board (the so-called through-mounting).

A special group is formed by the coaxial connectors provided withswitching contacts. This usually involves connectors in which the innercontact member is composed of two switching contact elements. Oneswitching contact element then functions as a contact member for makingcontact with a further connector, while the other switching contactelement forms an auxiliary contact member. In the state where noexternal contact is made, the two switching contact elements areelectrically connected to each other. This connection is automaticallybroken when contact is made with a further connector.

Connectors of this type are used, for example, in portable, wirelesstelephone sets which, in addition to their own built-in aerial, must beable to be connected to an external aerial, for example when used in avehicle. In the state where no external contact is made, thetransmission output of the telephone set is coupled, via the switchingcontact elements, with the aerial built into the set. In the state whereexternal contact is made, the switching contact element, which functionsas the inner contact member, connects the transmission output to anexternal aerial. Of course it is also possible for the outer contactmember only or for both the inner and the outer contact member to beprovided with switching contact elements.

As is known, care should be taken, when coupling RF coaxial wires, toensure that the characteristic impedances of the members to be connectedare substantially matched, in order to substantially limit lossesresulting from reflections and the like. This obviously also applies tothe connection elements employed, such as connectors and the like,which, in the case of mounting on a printed-circuit board, may beconnected directly to, for example, the transmitting stage on the board.

Coaxial connectors provided with means for impedance control or matchingare known from the prior art. See, for example, U.S. Pat. Nos. 3,873,785and 4,749,968. In order to achieve a desired impedance, use is made ofpassive electronic components such as resistors, coils and capacitorswhich are accommodated in the connector casing. In addition to the factthat these components take up relatively large amounts of space, whichhas an adverse effect on the dimensions of the connectors, it isdisadvantageous also from the assembly point of view to mount separateresistors, coils and the like in the connector casing and connect themelectrically to the contact members in question.

A coaxial connector as described in the first paragraph of thedescription is known from U.S. Pat. No. 5,222,149. The known device is adamping terminator for suppressing spurious current flow in highfidelity audio frequency equipment. The termination element includes aconductive-film-covered ferromagnetic-core electrical damping elementwhich is to be inductively coupled to potential signal carryingcomponents.

SUMMARY OF THE INVENTION

The object of the invention is, in the first instance, to provide acoaxial connector having facilities for impedance control or matching,without the use of electronic components such as resistors, coils,capacitors and the like.

According to the invention, this object is achieved by there beingdisposed in the connector a body of electroconductive material whichextends between the connection ends and is electrically separatedtherefrom, wherein the body of electroconductive material is providedwith connection means for connecting further electrical wiring, saidbody acting as a capacitive coupling between the connection ends therebyinfluencing the electrical connection impedance of the connector.

The body of electroconductive material essentially acts as a capacitivecoupling medium between the connection ends for the a.c. signals, orelectrical signals which reverse polarity in a different manner, whichare to be exchanged via the connector, and thus influences theelectrical connection impedance of the connector. A direct electricallyconducting connection of the body to the connection ends, as when usingseparate capacitors and the like, is unnecessary in the case of theconnector according to the invention. The degree to which theelectroconductive body influences the impedance depends, in a mannerknown per se, on the dimensions and the shape of the surfaces of thebody and the connection ends, as well as on the distance therebetween.The medium (dielectric) situated between the confronting surfaceslikewise affects the degree of capacitive coupling.

In a further embodiment of the coaxial connector according to theinvention, in which the inner and/or outer contact member comprisesswitching contact elements which, in a first position, make electricalcontact and, in a second position, are electrically separated, eachprovided with connection ends extending towards the connection side, thebody of electroconductive material extends between the connection endsof the switching contact elements and is electrically separatedtherefrom.

In addition to the capacitive coupling already mentioned, thisembodiment, in particular a version based thereon in which the body ofelectroconductive material is provided with a connection end forconnecting electrical wiring, in particular the signal earth, isadvantageous because mutual effective decoupling or, as the case may be,shielding of the switching contact elements is possible thereby. In thecase of the above-described use for wireless telephones, it is therebypossible to prevent, in the case of a connected external aerial,transmission energy leaking away to the aerial built into the telephoneset, which would mean a reduction in the range of the telephone whenused in a car or the like. This apart from losses due to mismatching andthe like. External interference signals which reach the switchingcontact elements are then likewise decoupled via the body in question.

In order to provide, in addition to a capacitive coupling, also acertain inductive coupling between the connection ends of the connector,there is arranged in the connector, in a still further embodiment of theinvention, a body of magnetic material which extends between theconnection ends and is electrically separated therefrom.

The magnetic material has an electrical effect comparable to aninductive element, such as a coil, connected in series to the connectionends or, as the case may be, the body of electroconductive material, butwithout the need for a direct electrical connection therewith.Especially in the case of telecommunication applications, the signalsexchanged via the connector are in general of such low strength thatonly a functional magnetic coupling arises in the vicinity of theconnection ends or, as the case may be, the electroconductive body, sothat there is no risk of undesirable radiation effects.

The degree of inductive coupling depends, inter alia, on the length overwhich the connection ends and/or the electroconductive body aresurrounded by the magnetic material and on the type of magneticmaterial. In order to substantially limit the hysteresis losses in themagnetic material, which arise under the influence of the a.c. signals,and in order to achieve, for signals of relatively low strength, aconnection or terminal impedance independent of the signal strength, theuse of magnetically soft material is preferred, preferably magneticmaterial having a high initial permeability, in particular ceramicmagnetic material or ferrite. One embodiment of the invention, which isadvantageous in terms of assembly, is that in which the body ofelectroconductive material and the body of magnetic material arecombined to form a single entity.

For the purpose of retaining the body of electroconductive material inthe casing, the body of magnetic material or a combined body, anembodiment of the connector according to the invention has connectionends designed as strips, with elements which are raised with respect tothe plane thereof and in the assembled state of the connector engage arelevant body.

An effective retaining action and, if required, accurate positioning ofthe body to be disposed between the connection ends are achieved, in oneembodiment of the invention, by the raised elements being lip-shaped andextending at an angle with respect to the associated plane, each havinga fixed resilient end and a raised free end, which free end in theassembled state engages the body in question, preferably in guide slotsor guide grooves formed for receiving therein the lip-shaped elements.

The raised elements can be punched as a whole from the strip-shapedconnection ends. The body of electroconductive material may likewisecomprise a strip-shaped conductor with elements which are raised withrespect to the plane thereof for retaining the electrical conductor in aduct in the material surrounding the conductor.

Especially for use in combination with a portable telephone set,according to an embodiment of the invention wherein the coaxialconnector is provided with a casing of electrically insulating material,there are accommodated in the casing, in addition to one or more coaxialcontact elements, also plug and/or socket contact elements. Via thisplug and socket contact elements it is then possible to exchangeexternal supply and other non-radio-frequency signals.

The coaxial connector according to the invention may be assembled in asimple manner, because direct electrical connections with theconnections ends of the contact elements are unnecessary. Consequentlythe invention also provides a method for assembling a coaxial connectoras described hereinabove, provided with a casing of electricallyinsulating material, the body being disposed in a first step between theconnection ends of the contact members in question, and in a furtherstep the assembly, thus formed, of contact members and body beingaccommodated from the connection side in the casing of the connector.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below in more detail with reference to adrawn embodiment of a coaxial connector provided with switching contactelements.

FIG. 1 shows, in diagrammatic form, a longitudinal section through acoaxial connector according to the invention, suitable for mounting on aprinted circuit board.

FIG. 2 shows, in diagrammatic form, a section along the line II--II ofthe connector depicted in FIG. 1, without casing.

FIG. 3 shows, in diagrammatic form, a view along the line III--III ofthe connector depicted in FIG. 1, without casing.

FIG. 4 shows, in diagrammatic form, a view of the contact side of acoaxial connector according to the invention, provided with a casing inwhich a plurality of plug and/or socket contact elements areaccommodated.

FIG. 5 shows, in diagrammatic form, a section along the line V--V of theconnector depicted in FIG. 4.

FIG. 6 shows, in diagrammatic form, a field of application of thecoaxial connector according to the invention, in particular theembodiment thereof depicted in FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment of the connector according to the invention depicted inFIG. 1 is of the socket type, provided with switching contact members,for mounting on a printed-circuit board.

The connector comprises a casing 1 of electrically insulating material,provided with a coaxial contact element 2 with a contact side 3 formaking contact with a further connector, and a connection side 4 formounting on a printed circuit board 5.

The contact side 3 is formed by an outer contact member 6 in the form ofa cylindrical sleeve of electroconductive material, which extends andflares out towards the connection side 4 and is provided with aconnection end 7 terminating in a soldering end for surface mounting onthe printed-circuit board 5. For the purpose of retaining the coaxialcontact element 2 in a clamping manner in the casing 1, the outercontact member 6 may be provided with a lip 8 and protuberances 9, thelip 8, in the mounted state, engaging with its free end on a stop 10formed in the casing. The casing 1 may, however, alternatively engagethe connection end 7 in a clamping manner in order to retain same by asufficient frictional force.

An inner contact member 11 extends coaxially within the outer contactmember 6 from the connection side 3. The inner contact member 11 and theouter contact member 6 are arranged to be electrically separated fromeach other by means of a body 12 of electrically insulating material.The inner contact member 11 consists, in the embodiment shown, of afirst switching contact element 13 and a second switching contactelement 14. The first switching contact element 13 has a contact end 15which adjoins a receiving opening 16 in the body 12 for making contactwith the inner contact member of a further coaxial connector (notshown). The second switching contact element 14 is provided with acontact end 17 which is situated in the casing 12 at a distance from thereceiving opening 16. The two switching contact elements 13, 14 areprovided with connection ends 18 and 19, respectively, which terminatein soldering ends for surface mounting on the printed circuit board 5.In the position where external contact is not made, or rest position,shown in FIG. 1, the two switching contact elements 13, 14 makeelectrical contact with each other.

In accordance with the invention there is situated, in the region of theconnector between the connection ends 18, 19 of the two switchingcontact elements 13, 14, a body 20 of electroconductive material which,in the embodiment shown, is surrounded by a sheath 21.

As can be seen clearly in the sectional view, depicted in FIG. 2, alongthe line II--II in FIG. 1, those sections of the connection ends 18, 19of the switching contact elements 13, 14 which are located in theconnector are constructed in the form of strips, and in particular asopposite flat plate sections between which the electroconductive body 20extends, the latter being likewise strip-shaped, and in particularformed as a flat plate 20, which can be seen in the view, depicted inFIG. 3, along the line III--III in FIG. 1.

For the purpose of retaining the body 20 or, as the case may be, thesheath 21, between the connection ends 18, 19 in the connector, theconnection ends 18, 19 are provided with lips 22 which, with their freeend, engage the sheath 21 which to this end is preferably provided withslots 23. The plate-shaped body 20 of electroconductive material isprovided in a similar manner with lips 24 which engage in a duct 25 inthe sheath 21 thereon. The body 20 is further provided with a connectionend 26 for connection to the printed-circuit board 5.

As can be seen clearly from FIG. 1, the electroconductive body 20 inconjunction with the connection ends 18 and 19, respectively, formsplate capacitors, the capacitive coupling mainly being a function of thearea of the opposite plate sections, the spacing therebetween and thematerial which is present between the plate portions. In radio-frequencyapplications, in particular, this capacitive coupling affects theimpedance which is perceived by an electrical signal from the connectionside 4 of the coaxial contact element.

Connecting the connection end 26 of the plate-shaped body 20 to, forexample, the signal earth achieves, in the state where contact is madewith a further connector and the electrical connection between the twoswitching contact elements 13, 14 being broken, a shielding effectbetween the two switching contact elements 13, 14. This supplementaryshielding effectively prevents crosstalk between the electricallyseparated switching contact elements 13, 14, which may arise especiallyin radio-frequency applications. External interference signals whichreach the connection ends 18, 19, in particular the section protrudingoutside the casing 1, are then likewise diverted to the signal earth viathe capacitively coupled electroconductive body 20. It will be evidentthat this promotes reliable functioning of the apparatus connected viathe coaxial connector according to the invention.

As diagrammatically indicated by dashed lines in FIG. 1, it is alsopossible to arrange a body of electroconductive material 27 between theconnection ends 18, 19 and the connection end 7 of the outer conductor6. The body 27 may, for example, entirely envelop the connection ends18, 19 or may be composed of separate loose parts, provided, if desired,with a connection end for mounting on the printed circuit board 5. Suchan electroconductive body 27 likewise results in an effect on thecapacitive coupling between the inner conductor 11 or, as the case maybe, the switching contact elements 13, 14, and the outer conductor 6,owing to which impedance matching is again possible. The body 27 may, ina similar manner to the body 20, be retained by means of lips in a ductformed in the body 12 (not shown).

In addition to a body 20 with sheath 21, or a body 27 ofelectroconductive material, respectively, it is also possible toaccommodate a body of magnetic material between the respectiveconnection ends for the purpose of varying the impedance via inductivecoupling. Ceramic, ferrimagnetic material is found to be particularlysuitable for this purpose. Soft magnetic ferrite material which has botha high initial permeability and a high electrical resistance ismanufactured by powder pressing followed by sintering. Such a body may,for example, be constructed in the form of the jacket 21 and be retainedtherebetween by means of the lips 22 of the connection ends 18, 19.

In combination with an electroconductive body 20, the sheath 21 beingmade of magnetic material, a partial capacitive and inductive couplingis possible by means of which, for example, the impedance of theconnector can be accurately tuned for certain frequency ranges. By usingweakly electroconductive material, an additional resistive coupling canbe accomplished if desired.

The coaxial connector according to FIG. 1 can be assembled in a simplemanner by accommodating, in a first step, the electroconductive body 20with its sheath 21 and/or a correspondingly shaped body of magneticmaterial of the same dimensions between the connection ends 18, 19 ofthe switching contact elements 13, 14 and then introducing the whole ina clamping manner into the body 12 from the connection side 4 of theconnector, whereupon the thus assembled entity can be accommodated inthe casing 1.

Instead of a coaxial connector for mounting on a printed-circuit board,as described and illustrated in the above, in particular for thetechnique of surface mounting, the principle of the invention can alsobe applied to so-called cable connectors, where the connection ends 18,19 are provided with suitable connection terminals for mountingelectrical cables. Connection techniques suitable for this purpose areknown per se in practice. It is of course also possible to mount theconnector via a pin/hole connection on a printed-circuit board insteadof by the surface mounting technique shown.

It will be evident that the principle of the invention can also beapplied to coaxial connectors provided with a pin-shaped orsocket-shaped inner contact member. The body of electroconductive and/ormagnetic material according to the invention then extends between theconnection ends of the inner contact member in question and the outercontact member of the coaxial connector, all this in accordance with thebody 27, indicated in FIG. 1 with dashed lines in the case of anelectrical conductor, and, for example, the use of a magnetic body 12 inthe case of an inductive coupling. Here, again, of course, combinationsof the two are conceivable.

FIG. 4 shows the view of the contact side of a coaxial connector 30according to the invention, in which, in addition to a coaxial contactelement 2, a plurality of plug and/or socket contact elements 28 areaccommodated in a common casing 29. FIG. 5 shows a section along theline V--V in FIG. 4.

A connector of this type is suitable, in particular, for use in wirelessequipment where it is necessary, in addition to a radio-frequency link,for example for connecting an external aerial, also to exchange supplyand control signals with the apparatus in question.

FIG. 6 shows an example of a wireless telephone 31 provided with abuilt-in aerial 32 and a transmitting stage 37 which can be connected,via a connector 30 according to the invention and a further connector33, to an external aerial 34 of, for example, a car 35. Via the contactelements 28 of the connector 30 it is possible to make connections, vialines 36, to a microphone, loudspeaker supply and other peripheralequipment such as a modem, fax and the like.

The invention is, of course, not limited to the application described inthe above for a wireless telephone but can be employed in all thosecases where a coaxial connector with options for impedance matchingand/or improved shielding against internal or external interferencesignals is necessary or desirable.

We claim:
 1. Coaxial connector provided with at least one electricalcontact element having a contact side in the form of a coaxial inner andouter contact member for making contact with a further connector, andhaving a connection side in the form of connection ends, which extendfrom the inner and outer contact member, for connecting electricalwiring, there is disposed in the connector a body of electroconductivematerial which extends between the connection ends and is electricallyseparated therefrom and the body of electrocondcutive material consistsof at least one electrical conductor surrounded by electricallynon-conductive material and the body of electroconductive material isplate-shaped.
 2. Coaxial connector according to claim 1, wherein theinner and/or outer contact member (11, 6) comprises switching contactelements (13, 14) which, in a first position, make electrical contactwith each other and, in a second position, are electrically separated,each provided with connection ends (18, 19) extending towards theconnection side (4), the body of electroconductive material (20) extendsbetween the connection ends (18, 19) of the switching contact elements(13, 14) and is electrically separated therefrom.
 3. Coaxial connectoraccording to claim 1, wherein the body connection means comprise aconnection end (26) extending towards the connection side.
 4. Coaxialconnector according to claim 1, wherein there is disposed in theconnector a body of magnetic material which extends between theconnection ends and is electrically separated therefrom.
 5. Coaxialconnector according to claim 4, wherein the body of electroconductivematerial (20) and the body of magnetic material are combined to form asingle entity.
 6. Coaxial connector according to claim 5, wherein thecombined body consists of an electrical conductor surrounded by magneticmaterial.
 7. Coaxial connector according to claim 1, wherein theconnection ends are strip-shaped and have a plane and have elementswhich are raised with respect to the plane of said connection ends suchthat, in the assembled state of the connector, said raised elementsengage the body of electroconductive material and the body of magneticmaterial, for the purpose of retaining it between the connection ends inthe connector.
 8. Coaxial connector according to claim 7, wherein thebody of electroconductive material (20) comprises a strip-shapedconductor having elements (24) which are raised with respect to theplane of said conductor, for retention thereof in a duct (25) in thematerial (21) surrounding the electrical conductor.
 9. Coaxial connectoraccording to claim 7, wherein the raised elements are lip-shaped, eachhaving a fixed resilient end and a raised free end, which free end inthe assembled state engages the body in question, preferably in guideslots or guide grooves formed for receiving therein the lip-shapedelements.
 10. Coaxial connector according to claim 1, provided with acasing (1) of electrically insulating material, further comprising plugand/or socket contact elements (2) accommodated in the casing. 11.Method of assembling a coaxial connector, said connector comprising acasing (1) of electrically insulating material provided with at leastone electrical contact element (2) having a contact side (3) in the formof a coaxial inner and outer contact member (11, 6) for making contactwith a further connector, a connection side (4) in the form ofconnection ends (18, 19), which extend from the inner and outer contactmember, for connecting electrical wiring and a body (20) which is madeof electroconductive and/or magnetic material and extends in the casingbetween the connection ends, wherein the body of electroconductivematerial (20) is provided with connection means for connecting furtherelectrical wiring, the body being disposed in a first step between theconnection ends of said contact members, and in a further step theassembly, thus formed, of contact members and body being accommodatedfrom the connection side in the casing of the connector.
 12. Coaxialconnector provided with at least one electrical contact element having acontact side in the form of a coaxial inner and outer contact member formaking contact with a further connector, and having a connection side inthe form of connection ends, which extend from the inner and outercontact member, for connecting electrical wiring, there is disposed inthe connector a body of electroconductive material which extends betweenthe connection ends and is electrically separated therefrom and there isa jacket of magnetic material which extends between the connection endsand is electrically separated therefrom and said jacket is integral withand surrounds the body of electroconductive material.